During the past year we investigated: a) The effect of monocrotaline treatment on 5-HT and norepinephrine removal by perfused rat lung. It was shown that monocrotaline reduced amine clearance by 50% and 60% respectively. b) The identification of 5-HT metabolites in isolated perfused rabbit lung by HPLC. It was shown that the primary metabolite in the effluent was 5-hydroxy indole-3-acetic acid. c) The clearance of 5-HT by human lung using an indicator dilution technique, in vivo. It was shown that human lung cleared 60% of administered 5-HT during a single passage through the pulmonary circulation. d) The effects of imipramine or cocaine on 5-HT and norepinephrine clearance by rabbit lung in vitro. Imipramine reduced 5-HT clearance from 79% to 60% and norepinephrine clearance from 57% to 19%. Cocaine had no effect on norepinephrine clearance. Cardiogreen served as the intravascular reference in these experiments. Our goals for 1980-81 include: a) studies on the clearance of angiotensin I by rabbit lung in vitro and in vivo. b) studies on the effects of physiologic- or drug-induced changes on the pulmonary conversion of angiotensin I to II, in vivo. c) studies on the effects of endotoxin shock in the pulmonary clearance of 5-HT and NE and pulmonary metabolism of angiotensin I.